In communication bus systems, such as a CAN-bus, galvanic isolation of the bus can be required in cases where e.g. the different boards (that communicate via the bus) have different earth potentials or the earth contains a disturbing amount of high frequency noise. Such galvanic isolation requires an isolated power supply for the bus communication system. However, if the isolated power supply on a particular board malfunctions, the bus communication of this particular board will fail. To reduce the risk of bus communication failure, each board may be equipped with two isolated power supplies such that if one fails the other one can maintain operation of the bus communication system. Another known approach is to provide one board with two isolated power supplies and let these provide power to the remaining boards via appropriate wiring. In both cases, the reliability is improved by a factor of 2, i.e. from Rel to 2*Rel (where Rel denotes the reliability of a single power supply).
However, in some applications involving a bus communication system, such as subsea power distribution systems for oil and gas extraction facilities, it is highly undesirable, if at all possible, to repair or replace a defective isolated power supply. It is desirable to design the aforementioned applications to have a life cycle of 20 years or more. This can only be achieved with a highly reliable power supply system for the communication bus.
Thus, there may be a need for a highly reliable isolated power supply system for bus communication units.